The present invention relates to a communication field, and particularly relates to miniaturization and configuration of a wide angle circular polarization antenna adapted for portable radio communication using a satellite.
Recently, plans of a portable telephone using a satellite have been proposed by some companies. A band of 1.6 GHz is allocated to communication (transmission) from a ground portable telephone to a satellite, and a band of 2.4 GHz is allocated to communication from the satellite to the ground portable telephone. The band of 1.6 GHz is also allocated as a frequency band used for bidirectional communication from the ground to the satellite and from the satellite to the ground.
An antenna adapted for such satellite communication, an omnidirectional antenna, is proposed in (JP-A-7-183719). FIG. 12 shows the structure of this omnidirectional antenna disclosed in the JP-A-7-183719.
In FIG. 12, a microstrip planar antenna (MSA) 1 is constituted by a feeding pin 1a, a patch-like radiating element 1b, and a dielectric substrate 1c. The MSA 1 is characterized such that a ground conductor plate 1d is extended downward to form a conductor cylinder 1e as a ground.
Usually, the MSA 1 has a configuration such that the patch-like radiating element 1b is arranged on the ground conductor plate 1d in parallel therewith through the dielectric substrate 1c. However, the omnidirectional antenna shown in FIG. 12 is characterized in such a way that the whole circumference of the ground conductor plate 1d is extended downward to form a cylindrical shape.
By this characteristic, in the omnidirectional antenna shown in FIG. 12, the ground conductor plate 1d of the microstrip planar antenna (MSA) 1 is extended downward to improve the gain at a low elevation angle.
In this omnidirectional antenna, however, it is difficult to obtain sensitivity of a horizontally polarized component of a circular polarization at a low elevation angle. Accordingly, in practical use, it is difficult to keep sensitivity of communication since trees or the like absorb a vertically polarized component.
The present invention discloses a plurality of planar radiating elements that are disposed under a ground conductor plate of a microstrip planar antenna and electrically coupled with the ground conductor plate.
Further, a plurality of planar radiating elements and a plurality of linear radiating elements are disposed under a ground conductor plate of a microstrip planar antenna and electrically coupled with the ground conductor plate. Further, a sperrtopf (blocking bushing) is provided. The xe2x80x9csperrtopfxe2x80x9d is a blocking bushing having a configuration in which a cylindrical conductor of xc2xc wavelength or xc2xd wavelength is provided to cover a coaxial line in a vicinity just under the feeding point of the antenna in order to prevent a leakage current from flowing in the outer surface of the outer conductor of the coaxial cable, the cylindrical conductor being opened on the antenna side while it is connected at the other side to the outer conductor of the coaxial line.